1. Field of the Invention
The present invention relates to a cooperative transmission method and a communication system using the same and, more particularly, to a cooperative transmission method capable of effectively reducing the quantity of transmission data while minimizing degradation of quality of service (QoS), and a communication system using the same.
2. Description of the Related Art
Recently, various techniques such as orthogonal frequency division multiplexing (OFDM), multiple input multiple output (MIMO), smart antennas, and the like, have been introduced to achieve a high data transmission rate. However, a request for a high data transmission rate in a state in which transmission power is limited may bring about an increase in an error rate and a reduction in a communication available distance. Thus, in order to solve this problem, research on a cooperative transmission method using a repeater is actively ongoing.
The cooperative transmission method using a repeater may be divided into an amplify-and-forward (AF) type cooperative transmission method and a decode-and-forward (DF) type cooperative transmission method. In the AF type cooperative transmission method, a repeater amplifies a signal which has been received from a terminal, and transmits the amplified signal to a base station, so the size of data transmitted in a second frame may be equal to the size of the data the terminal transmits to the base station. In the DF type cooperative transmission method, when an encoding scheme used in the repeater is used in the same manner as that of the terminal, the size of data transmitted in the second frame is the same. However, when a different encoding scheme from that used in the terminal is used in the repeater, the size of data transmitted in the second frame from the repeater to the base station can be adjusted. In this case, however, when the size of the data in the repeater is reduced, the QoS of the data received by the base station is degraded. Therefore, a method for effectively reducing the quantity of data transmitted in the second frame while minimizing degradation of QoS is required.